The present invention relates to a hydraulic damper, or damper-snubber combination which has a seal and bellows for capturing leakage from the seal and which also has an encircling coil spring assembly for carrying a load.
By way of background, dampers and damper-snubbers are shown in prior U.S. Pat. Nos. 4,638,895 and 4,768,627. These devices have seals for the shaft and, as explained in these patents, there is a certain amount of leakage of hydraulic fluid past these seals. However, in order to contain the leakage, metal bellows are used to capture the leaking hydraulic liquid and return it to the cylinders as the piston rod moves into the cylinders. The foregoing structure worked perfectly satisfactorily as long as there were no torsional forces exerted on the bellows which could wrinkle and tear it because of its fragile nature, considering that it was fabricated of thin, flexible metal. However, when dampers and damper-snubbers of the foregoing types were to be used with an encircling coil spring to carry a load, the spring could exert a torsional force between the piston rod and the cylinder and thus exert a torsional force on the bellows which could wrinkle and tear it. Various remedial constructions were suggested for compensating for the torsional forces produced by a single spring. These included providing a keyway between the piston rod and the seal and also the use of ball bearings at the ends of the springs. The keyway was deficient in that it exerted a frictional force on the assembly. Ball bearings also created a certain amount of friction, but more importantly, they added considerable expense to the structure.